mean solar time vs mean time

mean solar time and mean time both are nouns.

Word	Noun	Adjective	Verb	Adverb
mean solar time	Yes	No	No	No
mean time	Yes	No	No	No

As nouns, mean solar time and mean time are synonyms defined as:

mean solar time and mean time: (astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)

mean solar time (noun)	mean time (noun)
(astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)	(astronomy) time based on the motion of the mean sun (an imaginary sun moving uniformly along the celestial equator)